When workpieces, e.g. workpieces of sheet steel, are punched, a burr is frequently formed on the cutting edge of the die, projecting from the cutting edge of the die in the return stroke direction of the blanking punch. The nature and extent of the burring depend on various factors such as the material machined, the cutting geometry, and/or the condition of the tools used. After the punching process the workpiece, after being at rest during the preceding machining process, is displaced transversely to the direction of movement of the blanking punch, either to transfer it to the next machining position or to remove it from the machine after machining.
If, after machining, the workpiece is not raised a certain distance from the die and supported in a raised position, the workpiece slides in a displacement movement on a die surface that is aligned with the cutting edge in the displacement. During this movement, the burr projecting from the cutting edge of the die can cause scratches on the workpiece side facing the die, even if the burr projects only a few hundredths of a mm beyond the cutting edge.
To eliminate this drawback a method, among other things, is proposed in DE 297 02 699 U1 for movably supporting a work support on the base body of the die against the action of a restoring force in the machine stroke direction of the blanking punch. A work support supported by a spring on the base body of the die, for example, is proposed for this purpose. One problem that has arisen here is that in the case of heavy workpieces, the work support is forced downwards by the intrinsic weight of the workpiece and consequently the underside of the workpiece is again moved close to the cutting edge and even rests on the die surface. A burr on the cutting edge therefore again causes scratches on the underside of the workpiece. If stronger spring elements are used, the spring elements do not yield sufficiently during punching and the work support is pushed so strongly against the underside of the workpiece that lighter, and hence generally thinner workpieces are deformed during the punching process.
JP 07256367 A proposes that a brush table be used where the brushes are firmly arranged with one end on one plate and the other free end projecting through a second plate which runs parallel to the first plate end is vertically adjustable relative to the first plate. This measure can alter the stiffness of the brushes. In order to adapt the punching machine to workpieces of different weight the entire brush table must therefore be modified by adjusting the height of the plates relative to each other. Moreover, brushes suffer from the disadvantage that they wear. Finally, even in the arrangement presented in JP 07256367 A, the brushes may push through in the case of heavy workpieces and the workpiece may rest on the die, resulting in scratches.